Method of manufacturing a semiconductor device by plasma etching of a double layer

Abstract

A method of manufacturing a semiconductor device, in which a double layer consisting of a layer of polycrystalline silicon and a top layer of a silicide is applied to a surface of a semiconductor substrate coated with a layer of silicon oxide. After an etching mask has been provided, the double layer is etched in a plasma formed in chlorine gas to which up to 20% by volume of tetrachloromethane is added until the layer of polycrystalline silicon is etched. Thus, the double layer is etched anisotropically and the layer of silicon oxide is attacked in practice to a very small extent.

What is claimed is: 
     
       1. A method of manufacturing a semiconductor device comprising the steps of coating a surface of a semiconductor substrate with a layer of silicon oxide,   applying a double layer to said layer of silicon oxide, said double layer being a first layer of polycrystalline-silicon contacting said layer of silicon oxide and a second layer of a silicide on top of said first layer,   forming an etching mask on said double layer, said etching mask having openings to said double layer,   etching said double layer through said openings with an etching plasma of chlorine gas,   adding up to 20% by volume of tetrachloromethane to said chlorine gas said adding being sufficient to provide anisotropic etching of both the silicide and the polycrystalline-silicon, and   stopping supply of said tetrachloromethane to said chlorine gas after said polycrystalline-silicon has been partly etched and before said layer of silicon oxide is etched.   
     
     
       2. A method according to claim 1, wherein up to 10% by volume of hydrogen is added to said chlorine gas etching plasma after said step of stopping supply of said tetrachloromethane. 
     
     
       3. A method according to claim 1 or claim 2, wherein said second layer includes one of molybdenum silicide or tungsten silicide. 
     
     
       4. A method according to claim 3, wherein said etching plasma is produced by an electromagnetic alternating field having a frequency of 50 to 500 kHz. 
     
     
       5. A method according to claim 1 or claim 2, wherein said etching plasma is produced by an electromagnetic alternating field having a frequency of 50 to 500 kHz.